4 hours is plenty for your house, never mind a smaller rental flat. It does sound as though she is rushing your job as she has others.
I would remind her of what she needs to do every week, inc replacing plug covers & that she is paid for 4 hours so needs to do 4 hours & then review it again after a couple of weeks.
If there is no improvement, then I would say to her that you are considering letting her go & getting someone else & see what she says.
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